A mower head is the sub-assembly of a lawn mower that cuts the grass over which the lawn mower travels. At places where there are large areas of grass to be cut, such as at golf courses and parks, lawn mowers take the form of tractors to which a number of mower heads are attached. A typical mower head includes a frame to which the other components of the head are attached. One of these components is a reel, which is an assembly of spiral-shaped blades that functions as the actual cutting element for mowing the grass. A mower head also includes front and rear roller assemblies. Each roller assembly includes a roller body which is designed to roll on the ground over which the mower head travels. One of the roller assemblies is securely attached to the mower head frame; the other of the roller assemblies can be adjustably positioned up or down so as to allow the height of the blades to be selectively set. Typically, but not always a mower head is constructed so that the rear roller assembly is in a fixed position relative to the rest of the head, while the front roller assembly is adjustably mounted to the roller head frame so as to allow selective positioning of the reel and blades.
A problem with many mower heads is that their roller assemblies have proved to be difficult subassemblies to maintain. In order for a mower head to smoothly travel over the grass, its roller bodies must freely rotate. To date, it is common practice to design a roller assembly so that it has a shaft that is fixedly secured to the mower head frame and a roller body that is fitted for rotation around the shaft. To ensure that the roller body freely rotates, bearing assemblies fitted in the roller body function as low friction interfaces between the body and the shaft. A disadvantage of these roller assemblies is that, even with relatively limited use, the grass and dirt to which they are exposed enters their bearing assemblies. In order to maintain the desired low-friction interface, it is necessary to periodically remove these roller assemblies from the mower heads, and partially disassemble them in order to access the bearing assemblies for cleaning. Once the bearing assemblies are cleaned, the roller assemblies must be reassembled and reinstalled on the mower head. This task of having to essentially completely disassemble and reassembly roller assemblies as part of their maintenance has proved to be a labor-intensive activity that requires an inordinate amount of time to perform.
Another problem with these roller assemblies is that the bearing grease introduced into the roller body-shaft bearing assembly has been known to leak out of the roller bodies as these mower heads are used. This necessitates having maintenance personnel remove the grease from the turf on which it is deposited. Often though there is usually some grease left even after the turf is cleaned. This grease then adversely affects the turf and can cause environmental problems since it can easily become a ground water pollutant.
There have been attempts to reduce the efforts associated with having to maintain mower head roller assemblies by constructing them so that the roller bodies and shafts are formed as integral units that rotate in unison. These assemblies are mounted to the mower heads with which they are associated by bearing assemblies that are attached to structural elements of the mower head frame. These mounting structures have, to some extent, reduced the amount of time required to maintain these roller assemblies. These assemblies, however, have their own problems. In particular, problems arise because the bearing assemblies are attached to the structural elements of the associated mower head frames. Over time, as the mower heads are driven over and against hard objects such as tree stumps, rocks, and curbs, these structural elements become bent out of shape. The bearing assemblies attached to these elements fall out of alignment with each other. Once the opposed bearing assemblies holding a roller-and-shaft unit in position become out of align, the assemblies serve not to free the roller-and-shaft unit for rotation but, instead, inhibit the unit's movement. Thus, while, to date, roller assemblies with external bearings may have some reduced maintenance attributes, they are not without their own problems.
There are also disadvantages associated with the actual roller bodies of many roller assemblies. Some roller assembly bodies are made out of metal, such as steel or aluminum. As they are exposed to the elements, over time, these roller bodies have been known to corrode and rust. Still another problem with these bodies is that as they are passed over the hard objects that are in the paths of the mower heads, these assemblies become dented and sometimes lose their shape to the point of no longer being functional. There have been attempts to solve this problem by forming roller bodies out of rubber instead of metal. While rubber roller bodies do not corrode, they can, over time, become misshapen as a result of their own exposure to the hard objects over which a mower head travels. There have also been efforts made to form these rollers out of plastics. A problem with these efforts is that it has proved very difficult and expensive to manufacture the relatively long roller bodies, i.e., bodies of 18 inches and length and longer, that need to be provided for use with many commercial mower heads. Thus, to date, it has also been difficult to provide a roller assemblies with roller bodies that maintain their shape and utility for extended periods of time.